1. Field of the Invention
The present invention relates to an ink non-ejection detecting circuit of an inkjet printing apparatus, and a method for inspecting an inkjet recording apparatus, and more particularly it pertains to an ink non-ejection detecting circuit of an inkjet printing apparatus using piezoelectric elements for ejecting inks, a method for inspecting such an inkjet recording apparatus, and an inkjet recording apparatus.
2. Description of the Related Art
In recent years, so-called inkjet recording apparatuses in which inks are ejected from ink ejection nozzles are employed with numerous printers by virtue of the fact that they are featured by compactness and low cost. Of the inkjet systems, it is the piezo inkjet system in which ink ejection is carried out due to deformation of a piezoelectric element that is dominantly utilized from the standpoints of high resolution and high-speed printing performance.
In an inkjet recording apparatus using vibration energy of a piezoelectric element, it is arranged such that a piezoelectric element provided in an ink flow passage is vibrated in accordance with image information so that an ink droplet is formed due to deformation of the piezoelectric element. By controlling the waveform of a voltage applied to the piezoelectric elements, the meniscus at each ink ejection nozzle and resupply of ink after ejection can be controlled, and thus a high-frequency driving (ink ejection) and gradational recording by virtue of changing the quantity of ink droplets can be achieved.
In the operation of the inkjet recording apparatus described above, there is a likelihood that non-injection of ink will be caused because of air bubbles entering the ink supply portion from the nozzles and/or because of the ink adhered to the nozzle surface getting dried. In order to prevent such situations from occurring, it has been the usual practice that suction is frequently carried out with respect to the nozzle surface or maintenance such as wiping is serviced. Disadvantageously, this results in a useless consumption of a large amount of time and ink. Another disadvantage is that unless the maintenance is perfect, dot missing occurs, thus decreasing the quality of the printed matter.
Accordingly, it is conceivable to detect a nozzle in which ink non-ejection has occurred and perform a printing process using nozzles other than the nozzle in which ink non-ejection has occurred.
Methods for detecting a nozzle in which ink non-ejection has occurred have been proposed in JP-A Nos. 2000-355100 and 2000-318138, for example. In these methods, a nozzle in which ink non-ejection has occurred is detected based on a change of the resonance point of a piezoelectric element, and more specifically the resonance point of the piezoelectric element is detected by gradually changing the frequency.
A method for detecting a nozzle in which ink non-ejection has occurred without using a piezoelectric element as a driving source for ink ejection has been proposed in JP-A No. 2003-118093, for example.
However, the techniques disclosed in the above JP-A Nos. 2000-355100 and 2000-318138 are disadvantageous in that time is required to detect the resonance point since the resonance frequency of the piezoelectric element is detected by gradually changing the frequency.
Further, when use is made of a piezoelectric head using a piezoelectric element as a driving source for ink ejection, it is required to detect the resonance frequency of the acoustic-system admittance of the piezoelectric head comprising a piezoelectric element, a pressure chamber, an ink feed passage, and a nozzle wherein the influence of the electric-system admittance of the piezoelectric head is eliminated, in order to detect a state change due to an inflow of air bubbles and adherence of ink to the nozzle surface. The techniques disclosed in the above-mentioned JP-A Nos. 2000-355100 and 2000-318183 are problematic in that the accuracy of detection of a nozzle in which ink non-ejection has occurred is reduced because the resonance frequency of the piezoelectric element is being detected.
Another problem is such that when detecting the resonance frequency of the acoustic-system admittance of the piezoelectric head, difficulty is encountered in the detection of the resonance frequency since the SN ratio is low.